


Tenebris

by Yunica



Series: Pueritia Amicus [7]
Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Alternate Universe - Childhood Friends, Angst, Byleth the Assassin, Coercion, Edelgard and her siblings, Experiments, Gets dark, Hurt No Comfort, Implied/Referenced Torture, Slimy Arundel, Torture
Language: English
Status: Completed
Published: 2020-01-22
Updated: 2020-01-22
Packaged: 2021-02-27 10:34:19
Rating: Not Rated
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 3,078
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22355722
Author URL: https://archiveofourown.org/users/Yunica/pseuds/Yunica
Summary: Their idyllic days in the Empire come to an abrupt end.
Relationships: Edelgard von Hresvelg & My Unit | Byleth
Series: Pueritia Amicus [7]
Series URL: https://archiveofourown.org/series/1586014
Comments: 8
Kudos: 62





	Tenebris

**Author's Note:**

> TW: Torture, mentions of torture

The peace does not last. Byleth is the first to notice Arundel lurking in the shadows, observing them and Edelgard’s siblings if they were around, more and more often. She finds it odd, he had never shown this much interest in them before, and her instincts tell her to be more careful, attentive. Byleth listens to them for the first few weeks, staying more alert whenever he was nearby, but she slowly relaxes as he continues to passively idle on the side, believing her instincts to be wrong. They were not wrong.

Arundel finally approaches them, on the eve of the annual Spring festival. “Are you ready for the festivities to begin? You had best be watching out for them, I have heard that they will be quite the event this year.” Edelgard’s oldest sister offhandedly complains that it was always so hard to properly enjoy the shows since the crowds got quite large, and their father did not allow them special privileges just because they were royalty. 

“Don’t worry, I’ll be sure to save you all a front row seat.” Arundel speaks cryptically, and Byleth is not sure if he is referring to the festival tomorrow or something else. She shares her suspicions with Hubert, and he tells her that he would look into what Arundel had been doing recently. 

Before Hubert can begin to investigate, one of Edelgard’s older brothers disappears. It happens suddenly, he was there one day and then gone the next. There is no alarm, no announcement, no panic--besides the whispers between the other siblings. Some of the servants whisper and spread rumors, claiming they heard that he had fallen ill, but Byleth does not believe them. Edelgard’s siblings vanish one by one in quick succession after that, nothing but silence following in their wake. The stillness was eerie, even for Byleth, and for once, she wished it were not so quiet.

It was inevitable that they would eventually come for Edelgard, but when they finally do, Byleth does not let them take her quietly. Edelgard’s ajar door on an early morning sets Byleth off, and she immediately throws it open to see Arundel with four other people in dark robes, two of them holding Edelgard by the arms.

Byleth is on them before the door even slams against the wall, cleanly slicing off one of the arms gripping Edelgard. “Hands off,” she says shortly, voice steady and eerily calm, barely heard over the cloaked man she just dismembered screaming in agony. 

The other man holding Edelgard’s arm slackens his grip fearfully, beginning to back away when Byleth brandishes her sword at him with a flick. Edelgard’s frightened gaze meets her steady one, and she is moving forward. Arundel barks at him, "Do not be afraid of a child, fool!” but he still panics, and shoves Edelgard towards Byleth in an attempt to escape her attack. Byleth catches her easily with one arm, pushing Edelgard behind her and putting herself between the other girl and the small cohort in front of them.

Edelgard grips the back of Byleth’s shirt tightly, gathering courage from her presence. “Uncle, why are you taking my siblings?”

“For Fódlan’s future.”

“Fódlan’s future?...What do you mean?”

“You will understand in time. Now be good and come quietly.” Arundel boldly takes a step forward, and Byleth tenses, sword raised and ready again, but she is not prepared for the dark magic that sprouts from his hand. Byleth brings her arm higher in a vain attempt to shield both of them, but the blast throws her back, and she hears Edelgard call out to her as she slides across the ground, nearly colliding with the dresser across the room.

Byleth lashes out when two pairs of hands grab at her despite still being able to feel the spell burning her skin, but she buckles when they grab her injured arm and they easily hold her down. When she looks up, she can make out Arundel gripping Edelgard by the shoulder to prevent her from moving. The sight makes Byleth jolt and someone presses their knee into her back to stop her from moving.

Arundel’s hand tightens. “Control her, niece. If she continues to be a nuisance I cannot promise that drastic measures will not be taken.”

“Byleth, stop! They’ll keep hurting you if you don’t stop.” Byleth’s efforts weaken, but they do not stop completely.

Arundel gestures towards his men holding Byleth down. “Take her away, and find her a doctor. I am feeling gracious today. We would not want her to die from her injuries after all.” His smile is vile as he gives the commands. With renewed vigor, Byleth begins to pull at the hands grabbing her again at the notion of being separated from Edelgard, but she is shoved back into the floor, harder this time.

“Byleth! Please!” The desperate pleading in Edelgard’s voice finally seems to reach Byleth and she stops struggling. One of them lifts Byleth, throwing her over their shoulder. They are forced out of the room and brought in different directions, Arundel leading Edelgard one way and his men carrying Byleth another. Arundel guides Edelgard with a firm hand on her shoulder, preventing her from turning around to look at the cloaked men taking Byleth away.

Hubert passes by them in the hallway when they are almost to Byleth’s room, and it only takes a second before he shoves past them, breaking into a run towards Edelgard’s room. Byleth vacantly watches his figure disappear rapidly, but she knows that he is already too late.

They are descending down the stairs to the dungeons when Edelgard turns as much as Arundel allows her to look at him, gaze heated into a glare. “My father will put a stop to this. You won’t get away with this, uncle.”

Arundel lets out a laugh. “Your father? That man is nothing more than a puppet on a string. There is nothing anyone can do for any of you. You are mine now.”

* * *

Jeralt bursts into Byleth’s room, finding her bandaged and curled up in her bed. There is a look of unadulterated rage on her father’s face that she had never seen before, and she thinks for a moment that he is furious with her before he begins to curse Arundel, saying that he had always had his suspicions. This crossed the line.

“Hubert told me what happened. I’m getting you out of here, kiddo. We’re leaving immediately.” Jeralt kneels down, beginning to gather all of Byleth’s belongings. It does not take him long, she has never kept many personal things.

Byleth lifts herself up from the bed slightly, supporting her weight with her arm. “I’m not leaving, Father.”

“You can’t stay here Byleth.”

“I have to.”

“They almost killed you, Byleth. If you think I’m going to--”

“Dad!” Byleth's sudden outburst startles him, and the fact that she called him something other than Father, something more personal, makes him freeze. “You’re not listening to me. I can’t...I won’t run away and leave her here.”

“You can’t help her. Arundel is...he’s willing to do and use anything to get what he wants. He’ll send you out to do his bidding, and if you don’t he’ll use her against you.”

“I promised Edelgard I would stay by her side. I won’t let him scare me away.”

Jeralt looks at her, gaze hard. “That’s probably what he’s counting on.” 

Byleth stares back at him, just as resolute.

Jeralt could not deny that Byleth had changed for the better because of Edelgard, but something like this was...different. Were a few smiles here and there really worth putting Byleth's life in danger? He could just force her to leave, but he knows that she would find a way to make it back here regardless. So against his every paternal instinct, they stay.

* * *

Jeralt tries his best to stick around more, eyes watchful and poise tense. He admits to Byleth that they probably would not be able to run from Arundel, who was far more resourceful than he seemed. 

The only thing Byleth ever wants to do now is train, and so they train. The realization that she is useless and powerless to help Edelgard becomes overpowering if she sits around just waiting for something to happen, and knowing that Edelgard is suffering because of her weakness makes her train harder. She refuses to take breaks, moving to hit the dummies instead while Jeralt rests. 

Byleth uses Arundel’s peons as training dummies whenever Jeralt is not around. She never holds back, turning the fierce fire that burned inside her out on them instead. At first, he does not seem to care that she beats them around, simply supplying her more without much thought when one could not continue to participate anymore.

When Arundel tires of her ‘mishandling’ his henchmen and decides to direct her attention elsewhere, he begins to send her out on missions, handing her a missive with orders to assassinate a target. She refuses the first time, not wanting to do his dirty work. Arundel does not respond, and merely grabs her by the arm, forcing her to follow him. Byleth tenses when she realizes they are going down into the dungeons.

Going up to one of his scientists he tells them, “Grab Edelgard. I do not care who was on the schedule to be next, it is her turn now.”

The scientist runs off quickly to follow the command as Arundel pulls Byleth closer to him and asks, “Are you sure your answer is no, Byleth?” His grip tightens when she attempts to pull away. “Ah ah, you will miss the best part if you run away now.”

Byleth will never forget the sounds of Edelgard screaming and crying.

* * *

Edelgard does not know how many days--weeks?--have passed since those shadows brought her here and chained her up with her siblings. The last two of her siblings had been brought down soon after she was. Every day is filled with the sounds of screaming and crying, but Edelgard is not sure who is making the sounds anymore, which sibling it was.

They take turns experimenting on them. Each of her siblings gets a set amount of time on the table before being thrown back into their cell after a few shoddy healing spells, treated just enough so that they do not die to blood loss. They continue cutting into them during the next session if there is no success, regardless of if they had recovered enough or not.

At first she had tried resisting, anything to show that they did not hold any power over her, but then her uncle had brought Byleth down to the dungeons, and held a dagger to her neck. Byleth did not struggle because she knew that Edelgard would be punished if she did. Even after Edelgard stopped, they would occasionally remind her of what they could and would do to Byleth.

All Edelgard can think about is the fresh memory of a knife cutting into her flesh, a burning pain, and the terror that continues even when it is not her turn. Was no one going to save them? Each day she prayed to the goddess for salvation.

* * *

Byleth recognizes the meaning in Hubert’s eyes the first time she sees him, and she is not surprised that he blames himself. After all, she felt the exact same way. She had promised to protect Edelgard, but she is unable to save or help her, and knowing that she is being held right underneath their noses makes it worse.

The second time Byleth sees Hubert is after she returns from completing one of Arundel’s jobs, her target’s blood still splattered on her clothes. She does not stop when she passes by him, but he acknowledges her with his eyes as she walks by. They were both doing what little they could.

Byleth does not see Hubert much after those two times, both of them wallowing in their own misery at being unable to help Edelgard, who was the only thing that held them together. Granted, Byleth did not spend any time in the courts where he seemed to linger. She preferred to avoid seeing the people who had allowed this to happen to Edelgard, laughing and bickering about their idiotic politics. They were a joke. How was nothing being discussed about how the Emperor’s children were missing?

* * *

Even though they are all far too weak to escape after countless experiments, the shackles are never removed, keeping them chained to the walls and separate from each other. Edelgard’s siblings slowly begin to succumb to either their wounds or their own sanity. At the start, they would try their best to provide each other comfort, but as their numbers whittled and one by one they passed, silences began to stretch longer and longer. There were only the sounds of maddened muttering or whimpers. 

Their captors never bother to clean out the bodies until much later, as an afterthought. Rats gather to feast on the corpses, and sometimes one would skitter towards Edelgard. She barely has the strength to move away or deter the rats, and she is forced to listen as they skitter across the ground and chitter, eating away at her siblings.

They had started to become even rougher in their experiments, trying more methods in desperate hopes of procuring results because they were running low on test subjects and had yet to achieve success. One of her older brothers is the last to pass. He continues to whisper to her that everything is alright even as he lays dying. 

Edelgard is once again left to be the one missing them, but this time not even Byleth is there to be a balm for her loneliness. She finds herself craving for Byleth’s comforting presence, the sun on her skin, and the wind in her hair. Edelgard no longer prays to the goddess, her belief and faith shattered. If there truly was one, why would she allow such suffering?

* * *

Watching and observing is what Byleth does best, and she does a lot of it while studying her targets. She keeps a journal of all her targets, noting their schedules, weaknesses, likes and dislikes. Anything to give her information about them. She never makes a move until she is absolutely positive she can succeed. Most of the time she strikes out on her own, only requesting assistance from Jeralt if she deemed it absolutely necessary. It would do her no good to be on the receiving end of a killing blow. She had to stay alive if only for Edelgard’s sake. 

Byleth gains a title for the terror she brings to both Arundel’s associates and enemies. The Ashen Demon, a quick and efficient killer that leaves nothing in her wake. It did not matter if people worked under or against Arundel, they were terrified of her, knowing that her target could be any one of them. Her numb expression never gives anything away, and Arundel is not one to discriminate in who he killed. Even the smallest slights had him sending her after someone. Byleth never asks why, the reason was not important to her. She kills whatever she must so that she can stay by Edelgard, knowing that Arundel will dispose of her if she does not stay useful.

Arundel allows Byleth to see Edelgard briefly once. He praises her, and says it is a reward for successfully completing a mission for him, but Byleth knew it was just another reminder of the power he held over them. Regardless, the distance between them disappears almost instantaneously. Byleth fiercely embraces Edelgard, who startles at the contact, but reaches forward as far as the chains allow her to once she recovers, desperate for a familiar warmth.

* * *

The experiments do not stop just because she is the only left, all it meant was that the breaks in between the moments under the knife were shorter. Edelgard overhears the guards outside her cell speaking about the Tragedy of Duscur in the Kingdom, and her only thought is that more innocent people are dying at their repulsive hands. Had she and Byleth known a boy from the Kingdom?

To be honest, Edelgard doesn’t remember him. Perhaps a figment memory of a boy while they were there. She can hardly think of anything past the fog of pain and suffering the experiments bring whenever she tries to think back to the those times, so she always chooses to look forward towards the future. She focuses on thoughts of Byleth, knowing that she is also fighting for their future so that they can still be together after all of this. Edelgard instead thinks of the warmth she felt from Byleth when Arundel had let them see each other. She finds strength in knowing that Byleth is still here, and still fighting to be with her.

Today's session blends into the endless stream of red until one of the cloaked shadows around her makes a sudden exclamation, shouting about a success. Edelgard still does not know what their goal is, but there is clamoring and one of her experimenters runs off calling for a Thales, but the man who comes is her uncle. He stops in front of her and looks at her with glee. “You will be our greatest weapon, Edelgard,” her uncle, no Thales, tells her. He tells her that the crest they had been trying to get to manifest in her and her siblings had finally appeared in her after so long. The Crest of Flames. “You have done well to make it this far, my niece. I knew it would be you.” His hollow platitude.

They continue to study her even after the Crest of Flames manifests, wanting to know exactly why and how it did. The only difference is that they no longer cut into her, Thales now shouting at them to not waste such precious blood. They poke and prod at her, carefully taking small samples of her blood, and even strands of her hair, which is now a silvery white instead of the brown it was. 

Edelgard hates the Crest of Flames, and everything it represents. In the silence of her cell, Edelgard determines what she must do with this power, swearing to herself that she would do whatever it takes. She will never allow what happened to them happen to anyone else.


End file.
